Polymerization of butadiene



United States Patent Office 3,409,604 Patented Nov. 5, 1968 3,409,604POLYMERIZATION OF BUTADIENE Raymond A. Stewart, Jules Darcy, and LloydA. McLeod,

Sarnia, Ontario, Canada, assignors to Polymer Corporation Limited,Sarnia, Ontario, Canada, a body corporate and politic No Drawing.Continuation-impart of application Ser. No. 214,527, Aug. 3, 1962, whichis a continuation-in-part of application Ser. No. 36,120, June 15, 1960.This application is also a continuation-in-part of application Ser. No.114,631, June 5, 1961. This application Dec. 27, 1966, Ser. No. 604,610

Claims priority, application Great Britain, June 19, 1959, 21,148/59,Patent 917,401; Canada, June 28, 1960, 802,056, Patent 664,393

18 Claims. (Cl. 260-943) ABSTRACT OF THE DISCLOSURE This application isa continuation-in-part of our copending application Ser. 214,527, filedAug. 3, 1962, entitled, Polymerization of Butadiene, now abandoned,which is a continuation-in-part of application Ser. No. 36,120, filedJune 15, 1960, entitled, Polymerization of Butadiene, now abandoned, andclaims a Convention priority in Great Britain of June 19, 1959. Thisapplication is also a continuation-in-part of our copending application,Ser. No. 114,631, filed June 5, 1961, entitled, Polymerization ofButadiene, now abandoned and claiming a Convention priority in Canada ofJune 28, 1960.

This invention relates generally to the polymerization of conjugateddiolefins. It is particularly concerned with the polymerization ofbutadiene using a novel catalyst combination which produces a polymerthat is predominantly in the cis-1,4 configuration.

When butadiene is polymerized, the monomer units may enter the polymermolecule in a head-to-tail fashion in what is called a 1,4configuration. Alternatively, the units may enter the molecule in such away that only two of the carbon atoms become part of the backbone of thepolymer molecule, in which case the product is said to be in the 1,2configuration. The 1,4 configuration may be either cis-1,4 or trans-1,4depending on the configuration about the residual double bond. It haslong been recognized that the molecular structure of polybutadienedetermines its physical properties and it has been shown that theproduct having a high proportion of the units in the cis-1,4configuration has many properties similar to those of natural rubber andcan be used as a replacement for natural rubber in the production ofproducts such as heavy duty tires. It has even been established thatcis-1,4 polybutadiene is superior to natural rubber in some res ects.

It is already known that conjugated diolefins can be polymerized atrelatively low temperatures and pressures to produce high molecularweight polymers using a process involving a catalyst mixture of anorgano-metallic reducing agent and reducible compounds of heavy metals.These catalysts usually permit the production of polymers of controlledmolecular structure. It is known, for example, that when butadiene ispolymerized in the presence of a catalyst formed by mixing titaniumtetrabutoxide and aluminum triethyl, a product is obtained of which morethan is in the 1,2 configuration.

The object of the present invention is to provide a process for thepolymerization of butadiene to produce a polymer in which at least 75%,and preferably of the units are in the cis-1,4 configuration using acatalyst composition containing alkoxides of the heavy metals of GroupIV of the Periodic Table.

The term butadiene as used throughout this application refers tobutadiene-1,3 and is not intended to include butadiene-1,2 orderivatives of butadiene-1,3 such as chlorobutadiene or isoprene. ThePeriodic Table referred to is that shown in Handbook of Chemistry andPhysics, Chemical Rubber Publishing Company, Cleveland, Ohio, 33rdedition (1951).

The invention provides a process of producing a polymer of butadiene inwhich at least 75% of the units are in the cis-1,4 configuration whichcomprises polymerizing butadiene in the presence of a catalyst systemcomprising a mixture of a first component represented by the formulaTiCl,,(OR)., and a second component selected from the group consistingof (l) AlR' I and (2) a mixture of AlR and an iodine compoundrepresented by the formula XI, where R is a hydrocarbon radical having112 carbon atoms, R is selected from the group consisting of hydrogenand hydrocarbon radicals having 1-12 carbon atoms, n is a number from 0to 3, m is a number from 1 to 2, and X is selected from the groupconsisting of hydrogen, chlorine, bromine and iodine.

In one of its specific embodiments, the invention provides a process ofproducing polybutadiene containing at least 75% cis-1,4 addition whichcomprises homopolymerizing butadiene with a catalyst formed by mixingTi(OR) AlR land iodine, where R is a hydrocarbon radical having 1-12carbon atoms.

The alkoxides which can be used as the first component of the catalystsystem of the present invention may be represented by the generalformula TiCl,,(OR)., where R is a hydrocarbon radical such alkyl,cycloalkyl and aryl radical, and n is 0, 1, 2 or 3. The number of carbonatoms in the alkoxide radical is less than about 12 and the preferredcompounds are those containing 2-4 carbon atoms. Thus, examples of thealkoxides which may be used include titanium tetraalkoxides such astitanium tetramethoxide, titanium tetraethoxide, titaniumtetrapropoxide, titanium tetrabutoxide, titanium tetraoctyloxide,titanium tetranaphthyloxide; and chlorine containing titanium alkoxidessuch monochloro trimethyl titanate (TCl(OCH dichloro dimethyl titanate(TiCl (OCH trichloro monomethyl titanate (TiCl (OCH monochloro triethyltitanate (TiCl(OC H dichloro dipropyl titanate (TiCl (OC H trichloromonobutyl titanate (TiCl (OC H and various other ester groups withtitanium. It is understood, of course, that the hydrocarbon radicalcontaining 3 or more carbon atoms, may be any of the various isomerssuch as n-propyl or isopropyl. It is also to be understood that mixedradical alkoxides, for example, titanium diethoxide dibutoxide ormonochloro monomethyl rnonoethyl monobutyl titanate can be used withoutdeparting from the scope of the invention.

As noted above, a first group of compounds which may serve as the secondcomponent of the catalyst system and hence may be admixed with thetitanium alkoxides to form the catalyst system are compounds in whichthere are both a hydrocarbon radical and an iodine atom chemicallybonded or bound to aluminum. Such compounds may be represented by theformula AlR I in which R is a substituent selected from the groupconsisting of hydrogen andhydrocarbon radicals 'having 1-12 carbon atomsand m. is a number from 1 to 2. Examples of such compounds includealuminum diethyl monoiodide, aluminum monoethyl monoiodo hydride,aluminum monoethyl diiodide, aluminum diisobutyl monoiodide, aluminummonoisobutyl monoiodo hydride, aluminum monoisobutyl diiodide, aluminumdihexyl monoiodide, monoethyl aluminum monoisobutyl monoiodide,monohexyl aluminum monoisobutyl monoiodide, aluminum dibenzylmonoiodide, monobenzyl aluminum monoethyl monoiodide, and variouscombinations of other hydrocarbon groups with aluminum and with iodine.The size of the R radical is not critical although it is preferable touse those containing from 1 to 12 carbon atoms. R may be a tmonovalentaliphatic hydrocarbon or a monovalent aromatic hydrocarbon; the mostpractical of such compounds are saturated aliphatic hydrocarbon radicalshaving 2-8 carbon atoms.

As further noted above, the second component of the catalyst system maybe a mixture of a compound represented by the formula AlR' and iodine,iodine monochloride, iodine monobro-mide or hydrogen iodide. Theseiodine compounds may be represented by the general formula XI, where Xis H, Cl, Br or I. The compound of the formula AIR; may be any compoundin which is a substituent selected from the group consisting of hydrogenand hydrocarbon radicals having 1-12 carbon atoms. Examples of suchcompounds are aluminum triethyl, aluminum diethyl monohydride, aluminumtriisobutyl, aluminum di-isobutyl monohydride, aluminum dihexylmonohydride, monoethyl aluminum di-isobutyl, monohexyl aluminumdi-isobutyl, aluminum dibenzyl monohydride and monobenzyl aluminumdiethyl. Thus, R may be hydrogen or a monovalent aliphatic hydrocarbonor a monovalent aromatic hydrocarbon containing 1-12 carbon atoms, themost practical cases being those where R is a saturated aliphatichydrocarbon radical having 2-8 carbon atoms.

The aluminum compound may be in the form of an addition compound with apolar compound provided such addition does not result in seriouslowering of the yield or of the cis content of the product. For example,it is known that an ether, such as diisopropyl ether, forms acoordination compound with organo-aluminum compounds in this system, andit has been found that such etherates can be used in the practice of thepresent invention.

Catalyst systems may be prepared by mixing the alkoxide (it mayalternatively be called an ester) with a metal trialkyl and iodinatingthe mixture; such iodination may be effected by any suitable means usingiodine in -a reactive form. For example, titanium tetrabutoxide may bemixed in an inert atmosphere with aluminum triisobutyl to form acomplex. The complex may then be reacted with free iodine to produce aniodinated catalyst. Alternatively, aluminum triisobutyl may be reactedwith free iodine and the product of this reaction mixed with titaniumtetrabutoxide to form the catalyst complex. The reaction mechanism isnot fully understood but it is believed that the iodine replaces analkyl group on the complex or on the metal alkyl, depending on the orderof addition. The iodination may be effected using other compounds whichprovide iodine in a reactive or free form, including iodinemonochloride, iodine monobrornide and hydrogen iodide. The total amountof catalyst which is required to produce a satisfactory yield of polymerat a reasonable rate varies with polymerization variables such astemperature and purity of reactants and caribe determined readily bythose skilled in the art. However, the molar ratio of aluminum totitanium in the catalyst mixture is critical in that at least a minimumratio is required to effect polymerization. Thus, it is desirable to useratios greater than 1 and, while there is no theoretical upper limit, itis desirable for practical purposes not to exceed a ratio of about 10.When a chlorine containing titanium alkoxide'isused; the preferred ratioof aluminum to titanium is between 1.5 :1 and 6:1. In the catalystsystem based on titanium tetraalkoxide, the preferred ratio is from4.5:1 to 7:1.

In the production of the high cis-1,4 polybutadiene in accordancewith'the invention, it is essential that a small amount of iodine bechemically bound in the catalyst complex. It is surprising that thissmall change in the catalyst complex can convert a catalyst from onewhich produced predominantly 1,2 polybutadiene to one which producespolybutadiene containing more than 75% and frequently more than ofcis-1,4 product. The proportion ofbound iodine is conveniently expressedin terms of the aluminum present. The molarratio of iodine to aluminumis maintained between 0.25:1 and.2:l. Where the catalyst systemcomprises a mixture of a titanium alkoxide and a compound represented bythe formula AlR' I or comprises'a mixture of a compound of the formulaAlR and iodine it is found that in order to attain a polymer in which atleast 75 of the units are in the cis-1,4 configuration the molar ratioof iodine to aluminum in the catalyst system should be in the range of0.421 to 1.5 :1. When using a catalyst system comprising a mixture of acompound of the formula AlR' and iodine monochloride, iodine monobromideor hydrogen iodide polymers with a cis-1,4 content of at least 75% canbe obtained with iodine to aluminum ratios in the range of 0.25 :1 to1.521. The molar ratio of iodine to aluminum in the catalysts whichcomprise a mixture of titanium alkoxide with a compound of the formulaAlR I or a mixture of AlR with iodine is preferably in the range fromabout 0.821 to 1.5 :1. The iodinated catalyst complex may be obtained ina variety of ways. It may be prepared by mixing the alkoxide with any of(1) dialkyl aluminum monoiodide, (2) monoalkyl aluminum iodide, (3)mixtures of dialkyl aluminum monoiodide with monoalkyl aluminum diiodideand (4) mixtures of aluminum trialkyl with (1), (2) or (3). As mentionedpreviously, the catalyst complex may also be prepared by mixing andreacting alkoxide with aluminum trialkyl and iodinating the reactionproduct.

The polymerization may be carried out over a wide range of temperaturesvarying from about 25 C. to about C. although temperatures outside thisrange can be used without departing from the scope of the invention. Thepreferred operating range is between about 15 C. and +70 C. Thereactants may be dispersed in a non-reactive liquid medium such aspentane, hexane, heptane, cyclohexane, benzene or toluene or any otherrelatively low boiling non-reactive solvent which can be readily removedfrom the reaction product. It is usually preferable to use an amount ofsolvent such that the viscosity of the reaction medium permits readymixing and heat exchange. However, from the point of view of the productobtained, the proportion of solvent is not critical and it is evenpossible to operate in the complete absence of solvent in which casemonomeric butadiene acts as diluent. The method of addition of thecatalyst components to the polymerization system may be varied dependingupon the particular method of carrying out the polymerization and on theparticular components of the catalyst system. Thus, they may be added invarious orders, all at once or in increments or continuously during thepolymerization, provided the catalyst complex present duringpolymerization contains the specified proportion of bound iodine permole of aluminum. If the catalyst complex is formed in thepolymerization vessel, it is desirable that the components thereof beadmixed before the addition of butadiene. However, in such catalystpreparation, the components may be added in any order.

The invention will be described in greater detail by means ofexperimental results. The experiments were carried out using commercialgrade butadiene consisting of 96.5 to 98.5% butadiene-1,3 with thebalance including butane, butene-l, butene-Z and water. Unless otherwiseindicated, both the alkoxide and the metal alkyl were added asapproximately 1 molar solutions in heptane. Unless otherwise indicated,titanium tetrabutoxide contains the n-butyl isomer.

In the experiments, the diluent was dried either by distillation overaluminum triisobutyl or by treatment with calcium hydride, and butadienewas dried by passing it over alumina and calcium hydride.Polymerizations were carried out in standard seven ounce crown cappedbottles which had previously been thoroughly dried and flushed withnitrogen. The bottles, filled with nitrogen, were capped and thereaction components charged using a hypodermic needle inserted through arubber gasket. The bottles were maintained at a constant temperaturewhile polymerization proceeded. At the end of the desired period, thereaction was stopped by the injection either of an excess of ethanol orisopropanol and the product in each bottle was then transferred to aseparate flask and heated to 3550 C. for a period of one hour to removethe diluent and unreacted butadiene. The polymer was then extracted withboiling ethanol to destroy residual catalyst and dried under vacuum at50 C. for 16 hours. The conversion was calculated from the weight ofmonomer charged and the weight of polymer obtained. The structuralanalysis of the polymer was determined by means of an infra-redspectrophotometer. The analyses were based on the assumption that thepolymer contained one unsaturated bond for each monomer unit. Thestructure is shown in the following experiments as the 1,2 content andcis-1,4 content and it is to be understood that the balance of thematerial has a trans-1,4 configuration.

EXAMPLE I Butadiene was polymerized in the presence of a catalyst systemformed by admixing titanium tetrabutoxide with Al(C H 1. The reactantswere charged according to the following recipe:

Heptane-IS mls.

Titanium tetrabutoxide0.5 moles. Diethyl aluminum monoiodide-Variable.But'adiene15 mls.

TABLE I.POLYMERIZATION USING Ti(OC4Hn)4 AND A1(C2Hs)2I Run Al/Ti Conv.1,2 Content Sis-1,4 Number (Mole (Percent) (Percent (Percent Ratio) oftotal) of total) EXAMPLE II Butadiene was polymerized according to theinvention in the presence of a catalyst system prepared by reactingtitanium tetrabutoxide with aluminum triethyl and reacting the productformed thereby with free iodine. The catalyst was formed in thepolymerization bottle by first adding 10 mls. of pentane followed by 0.8ml. of a one molar solution of titanium tetrabutoxide in pentane and4.25 mls. of a one molar solution of aluminum triethyl in pentane. Themixture was allowed to age at room temperature for minutes after which9.2 mls. of a 0.25 molar solution of I in benzene was added and allowedto react for 45 minutes. The molar ratio of iodine to aluminum in thecatalyst system was thus 0.54. Then 30 mls. of butadiene were added andpolymerization allowed to proceed overnight at 30 C. A conversion of 80percent was achieved EXAMPLE III Butadiene was polymerized using acatalyst system prepared by reacting benzyl titanate with aluminumtriethyl and reacting the product formed thereby with iodine. Thecatalyst was formed in the polymerization bottle by first adding 10 mls.of heptane followed by one ml. of a one molar solution of benzyltitanate in pentane and 5 mls. of a one molar solution of aluminumtriethyl in pentane. Then 5.2 millimoles of iodine as a 0.25 molarsolution in benzene was added and allowed to react for 60 minutes. Themolar ratio of iodine to aluminum in the catalyst system was then 1.04.Then 25 mls. of butadiene were added and polymerization allowed toproceed overnight at 30 C. A conversion of 95 percent was achieved andthe product was found to contain 4 percent 1,2 material and 89 percentcis-1,4 material.

EXAMPLE IV Example III was repeated except that nonyl titanate was usedinstead of benzyl titanate. A conversion of 100 percent was achieved andanalysis of the product showed it to contain 6 percent 1,2 material andpercent cis-1,4 material.

EXAMPLE V Example III was repeated except that 2.8 millimoles of iodinemonochloride added as a one molar solution in benzene were used in thepreparation of the catalyst instead of iodine. The molar ratio of iodineto aluminum in the catalyst system was then 0.27. A conversion of 81percent was achieved and the product was found to contain 6 percent 1,2material and 81 percent cis-1,4 material.

EXAMPLES VI-X in Table II. In all cases, the 1,2 content was found to be5%.

TABLE II Diluent Buta- AI(C2H5)2I' Conversion (Dis-1,4

(M1s.) diene (Millimoles) (percent) (Percent (M1s.) of total) 15 30 1.8(4.5) 11 88 15 15 1.9 (4.8) 90 90 None 30 1.9 (4. 8) 62 93 40 15 2.3 (5.8) 96 85 40 20 3.5 (7.0) 100 80 *The figure in brackets shows the moleratio of diethyl aluminum monoiodide to titanium tetrabutoxide in therecipe.

EXAMPLE XI Butadiene was polymerized using a catalyst system formed byadmixing titanium monochlorotributoxide and aluminum diethylmonoiodide.The reactants were charged according to the following recipe and in theorder shown:

Heptane10 mls. TiCl(OBu) 1 10- moles.

Aluminum diethyl monoiodide-3 X 10 moles. Butadiene-25 mls.

EXAMPLE XII Butadiene was polymerized as in Example XI except that theamount of aluminum diethyl monoiodide was 4 10 moles. A yield of 14.2grams of polybutadiene 8 EXAMPLES XXIII TO XXV Butadiene was polymerizedusing a catalyst system formed by admixing titaniumtrichloromonobutoxide, aluminum triethyl and 1 The polymerizationrecipes used which analyzed as 79% cis-1,4, 13% trans-1,4 and 8% 1,2 areshown in Table V. material was obtained. TABLE v EXAMPLE XIII Example miu iir iiil i- (m iiligi ii: Butadiene was polymerized as in Example XIexcept moles) moles) moles) (11115) that the aluminum diethylmonoiodidewas replaced by 4 XXIII 40 1 2 gg millimoles of the diisopropyl etherateof aluminum trij' i8 5 i2, 1 ethyl and 2.16 millimoles of 1 The mixtureof the catay Components in heptane was aged for 45 minutes atPolymerization was carried out at C. for 16 hours room temperaturebefore the addition of the butadiene. 1F and the polymer recovered andtested as in previous exam. A Yield of grams of Polybutadiene whichanalyzed 0 ples. In Example XXIII, 7.4 grams of a product analyzing as16% trans'lfi and 7% 1,2 material was as 85% cis-1,4 was obtained. InExample XXIV, 1.3 grams l'fic v l' dof a polymer which was 79% cis-1,4was obtained and in EXAMPLES XIV AND XV Example XXV, 15 grams of apolymer which analyzed 20 as 86% cis-1,4 was obtained. Butadlene Wpqlymerlled P Example XI Xcept In order to determine whether iodine isessential for the that the alummum q q v was P m production of high cispolybutadiene using this catalyst 33216 XIV f 'Ymlhmoles of a111mmum,tr1ethyl and system, 20 ccs. of butadiene were polymerized usingthe minum)??? of lodlne f and m l XV same catalyst system as in ExampleXXIV except that the by {nflhmoles Of methyl and mlnlmoles 5 iodine wasomitted. 1.5 grams of polymer were obtained of lodme monochlorlde- Y 2and infra-red analysis showed it to be made up of 60% In both cases, 4.5grams of polymer which analyzed as c3474 material and 20% 1,2 material-Z32 (18 1,4, 16% trans 1,4 and 6% 1,2 material were ob EXAMPLES XXVI ToXXV In EXAMPLES XVLXIX 3O Butadiene was polymerized using a catalystsystem formed by admixing titanium trichloromonobutoxide, the Butadienewas polymerized using a catalyst system diisopropyl etherate of aluminumtriethyl and I accordformed by admixing titanium dichlorodibutoxide withing to the following recipe: aluminum triethyl and I according to thefollowing recipe: Heptane 40 mls Heptane-40 mls. 35 TiCl ,OBu'1 1Omoles. TiCl (Ol3u) 1 10- moles. Al(C H etherateVaria-ble. Aluminumtriethyl--Variable. I -Variable. I -Variable. Butadiene20 mls.Butadiene-2O mls.

The catalyst mixture was aged at room temperature The reactants wereadded in the order shown and after 40 after the addition of I and beforethe addition of the butathe addltlon 0f 2 the mlxtufe Was room lf diene.Polymerization was carried out for 16 hours at 30 ture for minutesbefore the addition of butadiene. C as i previous fimamples d thepolymer recovered d Polymerization was carried out at 30 C. for 12 hoursanalyzed The results are Shown in Table after which the polymers wererecovered and tested. The TABLE VI data are shown in Table III. 45

TABLE 111 Example (mil li- (51: 5 stmctme (percent) Al(C zHs)a I: YieldStructure (percent) 5, 3% moles) C154,; Trim-54,4 Example (inilli-(nulli- (gms) moles) moles) Cis-1,4 Trans-1,4 1,2 XXVI 2 L1 113 91 5 4XXVII 3 1.6 12.6 90 5 5 g a i Xxv1rr.. a 2.0 12.3 as 6 s 3 2.0 11.4 90 s4 4 82 14 4 The examples are intended to illustrate the invention andnot to unduly limit it. In this respect, the heavy metal In order todetermine whether iodine is essential for the r compounds Shown in theexamples Contain the butyl radiproduction of high cis polybutadieneusing this catalyst However, the butyl radical y be replaced y ethyl,system, 20 ccs. of butadiene were polymerized using the P PYL y xyl andthe like and the inventorshave same catalyst as in Example XVI exceptthat the iodine even found that m y cyclohexyl and p y TadiCals wasomitted. 6.2 grams of polymer were obtained which can be used: y, itould be understood that alanalyzed as 34% cis-1,4 and 40% 1,2. gq the pe show n m compounds c n- 60 taining the ethyl radical, this can bereplaced by other hy- EXAMPLES XX TO XXII drocarbon radicals such asbutyl, isobutyl, hexyl and octyl Butadiene was polymerized using thesame recipe as in radlcal' Examples XVI-XIX except that the diisopropyletherate W6 61mm: of aluminum triethyl was used instead of aluminum tri-A Process of Producmg, lf butadlene ethyl. The polymerization wascarried out and the poly- 6a wh ch at least 75% of the units 3,116 111the (HS-1,4 configumers recovered and tested as in Examples XVI-XIX andTimon Whlch comprises polymerwqe butadlfme the the data areshowninTab1eIV presence of a catalyst system comprising a mixture of a TABLEIv first component represented by the formula T1Cl (OR) and a second1component dselected from the group consist- AltCzHna Yield Structure (ping of (l) A R I an (2) a mixture of AlR and an Example (gms') (3154ATWIN; 1,2 iodine compound represented by the Formula XI, where moles) Ris a hydrocarbon radical having 1-12 carbon atoms, R XX 2 L1 no 88 q 3is selected from the group consisting of hydrogen and ggg i g; ghydrocarbon radicals having 1-12 carbon atoms, n is a number from 0 to3, m is a number from 1 to 2, and X is selected from the groupconsisting of hydrogen, chlorine, bromine and iodine.

2. The process according to claim 1 in which the second catalystcomponent is AlR' I.

3. The process according to claim 1 in which the second catalystcomponent is a mixture of AlR' and I 4. The process according to claim 1in which the second catalyst component is a mixture of AlR' and ICl.

5. The process according to claim 1 in which the molar ratio of iodineto aluminum in the catalyst system is between 0.25:1 and 2: 1.

6. The process according to claim 3 in which the molar ratio of iodineto aluminum in the catalyst system is in the range of 0.4:1 to 1.5: 1.

7. The process according to claim 1 in which R is an alkyl radicalhaving 2-8 carbon atoms.

8. The process according to claim 7 in which R is ethyl radical.

9. The process according to claim 1 in which the first catalystcomponent is a titanium alkoxide containing 1 to 3 chlorine atoms.

10. The process according to claim 9 in which the amount of the iodinecompound is between 0.5 and 1.5 moles per mole of organo-aluminumcompound.

11. The process according to claim 10 in which the molar ratio ofaluminum to titanium in the catalyst system is greater than 1:1.

12. The process according to claim 11 in which the molar ratio ofaluminum to titanium in the catalyst system is between 1.5:1 and 6:1.

13. The process according to claim 1 in which the first catalystcomponent has the formula Ti(OR) 14. The process according to claim 13in which the molar ratio of aluminum to titanium is between 3 and 10.

15. The process according to claim 14 in which the molar ratio ofaluminum to titanium is between 4.5:1 and 7: 1.

16. The process according to claim 13 in which R is a butyl radical.

17. The process according to claim 1 in which butadiene is polymerizedat a temperature within the range of 25 C. to +100 C. in the presence ofa non-reactive liquid and the polymer thereby produced is recovered fromthe reaction mixture.

18. A process of producing polybutadiene containing at least cis-l,4addition which comprises homopolym- IeriZing butadiene with a catalystformed by mixing Ti(OR) AlR and I where R is a hydrocarbon radicalhaving 1-12 carbon atoms.

References Cited UNITED STATES PATENTS 2,959,576 11/1960 Payne 26094.9

FOREIGN PATENTS 917,401 2/1963 GreatBritain. 664,393 Canada.

JOSEPH L. SCHOFER, Primary Examiner. R. A. GAITHER, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,409,604 November 5, 1968 Raymond A. Stewart et a1.

It is certified that error a pears in the above identified patent andthat said. Letters Patent are hereby corrected as shown below:

Column 2, line 50, after "such" insert as same line 50, "('ICl(OCHshould read (TiCl(OCH Attest:

Edward M. Fletcher, Jr.

' Attesting Officer WILLIAM E. SCHUYLER, JR.

Commissioner of Patents

